Softness and flexibility are key attributes for tissue and absorbent articles. One method to enhance softness or flexibility in these products is to add a softening agent such as silicone. Typically, the softening agent is added to the pulp fibers through a pretreatment or, for some tissues, applied topically to the outer surface. When using silicone pretreated pulp in tissues, the softness gain may be further enhanced through layering the fibers. Although the softness and flexibility gain from adding silicone additives is advantageous, this class of additives tends to have incomplete retention on the fibers, tends to be hydrophobic and may cause problems with absorbency. Due to the absorbency limitations, there has been much work on developing the chemistry and application of wettable silicones. Although these alternative silicones have helped to mitigate absorbency problems, they have also aggravated the retention efficiency. For example, a portion of the wettable softening agent may desorb from the pretreated fibers when in contact with water or body fluid.
For tissue machines, the unretained softening agents are recirculated through a “short-loop” water recirculation and may contaminate other fibers, fabrics, and creping surfaces. This is especially troublesome for layered tissue products where softening agents are desired on the outer layers and strength agents are desired in the center of the product. For absorbent articles, the unretained silicone reduces surface tension and can interfere with wicking, and superabsorbent particle capacity.
Thus, a need currently exists for a method of improving the retention of softening agents on pretreated pulp. For instance, a need currently exists for a method of improving the retention of wettable silicones on cellulosic fibers used in the production of tissue products and other absorbent articles.